Escherichia coli like most organisms adapts its fatty acid composition in response to growth temperature. Alcohols intercalate into membranes changing their viscosity (fluidity) in a fashion analogous to a change in temperature. We have found that both E. coli and mammalian cells in culture change their fatty acid composition during growth in the presence of alcohols. The purpose of this proposal is to investigate the mechanism by which drugs induce changes in lipid composition, the significance of these changes to cellular functions (adaptive?) and the generality of drug-induced changes in other systems. These studies will involve an investigation of alcohol effects on lipid synthesis, membrane structure and membrane-bound enzyme function primarily in E. coli. A model will be developed for the mechanism of drug-induced changes in lipid composition. Portions of this model may prove applicable to temperature-induced changes in E. coli and in other systems. Drug-induced changes in membrane lipids may also be related to the developement of tolerance to CNS-depressants.